In this paper, friction stir welding technique was used to join ferritic stainless steels, AISI 430. Ferritic stainless steel sheets were successfully joined considering both, the appearance of the welding bead and the strength of the welded joint by selecting proper weld parameters and tool material. The weld parameters such as revolutions, traverse speeds, compressive tool forces and tool tilt angles influenced the tensile strength of welded joints. Genetic algorithm model was developed to perceive the stronger joints by selecting proper welding parameter combinations. The strong welded joint higher than base material was obtained with appropriate welding parameter combinations, having a revolution of 1,120 rpm, compressive tool force of 4.5 kN, traverse speed of 125 mm min(-1), and tool tilt angle of 0 degrees. Best welding parameter combinations resulted in ultra fine grain structures in the welding zone and high-quality welded joint.